package com.thx.common.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;

/**
 * des 加解密工具.
 */
public class EncrypDesUtil {

  private static final Logger log = LoggerFactory.getLogger(EncrypDesUtil.class);

  private static String DES_ALGORITHM = "DES";
  private static String KEY = "SXTHXDES";

  /**
   * DES加密.
   */
  public static String encryption(String plainData)
      throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException,
      BadPaddingException, IllegalBlockSizeException {

    Cipher cipher = null;
    cipher = Cipher.getInstance(DES_ALGORITHM);
    cipher.init(Cipher.ENCRYPT_MODE, generateKey(KEY));

    // 为了防止解密时报javax.crypto.IllegalBlockSizeException:
    // Input length must be multiple of 8 when decrypting with padded cipher异常，
    // 不能把加密后的字节数组直接转换成字符串
    byte[] buf = cipher.doFinal(plainData.getBytes());
    return Base64Utils.encode(buf);
  }

  /**
   * DES解密.
   */
  public static String decryption(String secretData)
      throws NoSuchPaddingException, NoSuchAlgorithmException, BadPaddingException,
      IllegalBlockSizeException, InvalidKeyException {

    Cipher cipher = null;
    cipher = Cipher.getInstance(DES_ALGORITHM);
    cipher.init(Cipher.DECRYPT_MODE, generateKey(KEY));

    byte[] buf = cipher.doFinal(Base64Utils.decode(secretData.toCharArray()));
    return new String(buf);
  }


  /**
   * 获得秘密密钥.
   */
  private static SecretKey generateKey(String secretKey) throws NoSuchAlgorithmException {
    // SecureRandom secureRandom = new SecureRandom(secretKey.getBytes());
    SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
    secureRandom.setSeed(secretKey.getBytes());
    // 为我们选择的DES算法生成一个KeyGenerator对象
    KeyGenerator kg = null;
    try {
      kg = KeyGenerator.getInstance(DES_ALGORITHM);
      kg.init(secureRandom);
      // kg.init(56, secureRandom);

      // 生成密钥
      return kg.generateKey();
    } catch (NoSuchAlgorithmException ex) {
      log.error("", ex);
      return null;
    }
  }


  static class Base64Utils {

    private static char[] alphabet =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray();
    private static byte[] codes = new byte[256];

    static {
      for (int i = 0; i < 256; i++) {
        codes[i] = -1;
      }
      for (int i = 'A'; i <= 'Z'; i++) {
        codes[i] = (byte) (i - 'A');
      }
      for (int i = 'a'; i <= 'z'; i++) {
        codes[i] = (byte) (26 + i - 'a');
      }
      for (int i = '0'; i <= '9'; i++) {
        codes[i] = (byte) (52 + i - '0');
      }
      codes['+'] = 62;
      codes['/'] = 63;
    }

    /**
     * 将原始数据编码为base64编码.
     */
    public static String encode(byte[] data) {
      char[] out = new char[((data.length + 2) / 3) * 4];
      for (int i = 0, index = 0; i < data.length; i += 3, index += 4) {
        boolean quad = false;
        boolean trip = false;
        int val = (0xFF & (int) data[i]);
        val <<= 8;
        if ((i + 1) < data.length) {
          val |= (0xFF & (int) data[i + 1]);
          trip = true;
        }
        val <<= 8;
        if ((i + 2) < data.length) {
          val |= (0xFF & (int) data[i + 2]);
          quad = true;
        }
        out[index + 3] = alphabet[(quad ? (val & 0x3F) : 64)];
        val >>= 6;
        out[index + 2] = alphabet[(trip ? (val & 0x3F) : 64)];
        val >>= 6;
        out[index + 1] = alphabet[val & 0x3F];
        val >>= 6;
        out[index + 0] = alphabet[val & 0x3F];
      }

      return new String(out);
    }

    /**
     * 将base64编码的数据解码成原始数据.
     */
    public static byte[] decode(char[] data) {
      int len = ((data.length + 3) / 4) * 3;
      if (data.length > 0 && data[data.length - 1] == '=') {
        --len;
      }
      if (data.length > 1 && data[data.length - 2] == '=') {
        --len;
      }
      byte[] out = new byte[len];
      int shift = 0;
      int accum = 0;
      int index = 0;
      for (int ix = 0; ix < data.length; ix++) {
        int value = codes[data[ix] & 0xFF];
        if (value >= 0) {
          accum <<= 6;
          shift += 6;
          accum |= value;
          if (shift >= 8) {
            shift -= 8;
            out[index++] = (byte) ((accum >> shift) & 0xff);
          }
        }
      }
      if (index != out.length) {
        throw new Error("miscalculated data length!");
      }
      return out;
    }
  }
}
